For cutting tools of steel or cast iron, WC-based cemented carbide is widely used, but there has been a variety of proposals in order to reduce the tungsten usage, which is a rare metal, and obtain desired cutting performance.
For example, Japanese Patent No. 5185032 proposes a composite sintered body cutting tool made of a base material obtained by laminating a cemented carbide layer and a cermet layer which includes 15% to 65% by mass of WC and W in total and includes Co accounting for 80% by mass or more of iron group metals in bonded phases, in which, when the maximum thickness of the base material in the lamination direction is represented by h1, and the maximum thickness of the cutting edge portion in the lamination direction of the cemented carbide layer is represented by h2, h2/h1 is set to 0.002 to 0.02, thereby improving shock resistance and finished surface gloss.
In addition, for example, Japanese Patent No. 5297381 proposes a composite sintered body cutting tool made of a base material obtained by laminating a cemented carbide layer and a cermet layer which includes 15% to 65% by mass of WC and W in total and includes Co accounting for 80% by mass or more of iron group metals in bonded phases, in which protrusions and recesses having a maximum level difference of 50 μm to 500 μm are formed in the boundary between the cemented carbide layer and the cermet layer, and, when the maximum thickness of the base material in the lamination direction is represented by h1, and the maximum thickness of the cemented carbide layer disposed on the rake face side in the lamination direction is represented by h2, h2/h1 is set to more than 0.02 and 0.4 or less, thereby improving the joining properties between the cemented carbide layer and the cermet layer and preventing the deformation of the base material after sintering.
In addition, for example, Japanese Patent No. 5413047 proposes that, in the production of a tool body by forming a pressed compact of cemented carbide powder and a pressed compact of cermet powder respectively, laminating these pressed compacts together, and carrying out sintering by holding the laminate in a vacuum atmosphere at 1,300° C. to 1,500° C. for 0.5 to 3 hours, the unevenness state in the boundary between the cemented carbide layer and the cermet layer is set in a specific range or the amounts of bonded phases in both layers are adjusted to be in a specific range, thereby enhancing the joining properties between the cemented carbide and the cermet, preventing deformation caused during sintering, and improving the wear resistance and the toughness of composite sintered body cutting tools.